The present invention relates generally to apparatus and methods for removing occluding materials from body lumens. More particularly, the present invention relates to the construction and use of atherectomy catheters for excising atheroma and other materials from blood vessels.
Cardiovascular disease frequently arises from the accumulation of atheromatous material on the inner walls of vascular lumens, particularly arterial lumens of the coronary and other vasculature, resulting in a condition known as atherosclerosis. Atherosclerosis occurs naturally as a result of aging, but may also be aggravated by factors such as diet, hypertension, heredity, vascular injury, and the like. Atheromatous and other vascular deposits restrict blood flow and can cause ischemia which, in acute cases, can result in myocardial infarction. Atheromatous deposits can have widely varying properties, with some deposits being relatively soft and others being fibrous and/or calcified. In the latter case, the deposits are frequently referred to as plaque.
Atherosclerosis can be treated in a variety of ways, including drugs, bypass surgery, and a variety of catheter-based approaches which rely on intravascular widening or removal of the atheromatous or other material occluding a blood vessel. Of particular interest to the present invention, a variety of methods for cutting or dislodging material and removing such material from the blood vessel have been proposed, generally being referred to as atherectomy procedures. Atherectomy catheters intended to excise material from the blood vessel lumen generally employ a rotatable and/or axially translatable cutting blade which can be advanced into or past the occlusive material in order to cut and separate such material from the blood vessel lumen. In particular, side-cutting atherectomy catheters generally employ a housing having an aperture on one side, a blade which is rotated or translated by the aperture, and a balloon or other deflecting structure to urge the aperture against the material to be removed.
Although atherectomy catheters have proven to be very successful in treating many types of atherosclerosis, some catheter designs suffer from certain limitations. For example, many side-cutting atherectomy catheters have difficulty in capturing occluding material in the cutting aperture. To facilitate material capture, the cutting aperture is frequently elongated. Although improving material capture, such lengthening makes it more difficult to introduce the distal end of the catheter through torturous regions of the vasculature. Additionally, it is often difficult for conventional atherectomy cutters to apply the requisite pressure to cut off the targeted material. When higher pressures are applied, damage to the artery (barotrauma) can occur. High pressures can also compress plaque, subsequently reducing the cutter""s ability to capture the occlusive material. This decreases the effectiveness of these cutters and limits the cutter and catheter designs.
For these reasons, it is desired to provide atherectomy catheters which can access small, tortuous regions of the vasculature and which can remove atheromatous and other occluding materials from within blood vessels in a controlled fashion with minimum risk of injuring the blood vessel wall. In particular, it is desired to provide atherectomy catheters which can facilitate capturing of occlusive material. It would also be particularly desirable to decrease the amount of force required to cut off occlusive material from the body. At least some of these objectives will be met by the catheter and method of the present invention described hereinafter and in the claims.
The present invention provides catheters, kits, and methods for removing material from a body lumen. The catheters and methods of the present invention are for use in a variety of body lumens, including but not limited to intravascular lumens such as the coronary artery and other blood vessels. In general, the catheter of the present invention has a cutting element that cuts material engaged by a material capture device on the catheter body. Preferably, the material capture device tensions the material during cutting, which reduces the amount of cutting force required. The material capture device typically follows a path that draws material into the catheter body. Preferably, but not necessarily, the material capture device is arranged on the catheter body to advance along a path outwardly from the catheter body into the material and then inwardly towards the catheter body to tension the material. In some embodiments, the material capture device may extend in an outwardly direction but not beyond the outer diameter of the catheter body. The cutting element on the catheter body moves between a first position and a second position to cut the material while in tension, where motion of the cutting element urges the material capture device to draw cut material into the catheter body.
Desirably, the blade or blades of the catheter will be actuable with the application of reasonable mechanical forces which are capable of being transmitted along even rather lengthy catheters. Further desirably, the catheters will be suitable for directional removal of occluding material and may include mechanisms for engaging cutting blades against selected portions of a vascular wall. Optionally, the engaging mechanisms should permit blood perfusion during performance of an atherectomy procedure.
In one embodiment, the catheter of the present invention uses a material capture device in the form of a material capture needle. The needle will be deployed in a radially outward direction from the catheter body. Preferably, but not necessarily, the needle will capture material while the catheter remains stationary. Some embodiments may use a plurality of material capture needles. The material capture needle may follow a path outwardly from the catheter body in various manners. In one embodiment, the needle has a portion that advances through an elongate slot on the catheter body to move the needle along a path outwardly from the catheter body. Another embodiment uses a curved needle rotatably mounted about a pivot pin. As the needle is rotated, it will protrude outwardly from the catheter body. A preferred embodiment uses a needle having a bias element which urges the needle outwardly when the catheter is in position. Typically, a material cutting element will engage the material that has been captured and sheer off the material into the catheter.
In a further embodiment, a material capture device of the present invention uses a penetrating member mounted to extend through an aperture on the catheter body to penetrate material in advance of the cutting blade and to draw material into the catheter body as the cutting blade is advanced past the aperture. The penetrating member is rotatably mounted to the slidable cutting blade on the catheter body. A cam surface on the catheter body engages a surface of the penetrating member to guide the member along a path to engage the material and draw the material into the catheter body. In a still further embodiment, an abutment or raised portion on the catheter body is mounted to engage one end of the penetrating member. This contact caused the penetrating member to rotate about its pivot point on the cutting blade and thus engage material and draw material into the catheter body.
In another aspect of the present invention, a method is provided for excising occlusive material from within a body lumen. The method involves engaging the occlusive material with a material capture device on a catheter body. The material is drawn in a radially inward direction by the device to tension the material to be cut. A blade is advanced through the tensioned material to sever the material. from the body lumen. As mentioned previously, tensioning the material reduces ,the amount of cutting force required. The tensioning of the occlusive material may also comprise moving the material capture device towards a catheter body while the material capture device is in contact with the occlusive material. Typically, the engaging and tensioning steps may also be performed with a single motion by the user to facilitate cutting.
In a still further aspect, kits according to the present invention will comprise a catheter having a material capture device. The kits will further include instructions for use setting forth a method as described above. Optionally, the kits will further include packaging suitable for containing the catheter and the instructions for use. Exemplary containers include pouches, trays, boxes, tubes, and the like. The instructions for use may be provided on a separate sheet of paper or other medium. Optionally, the instructions may be printed in whole or in part on the packaging. Usually, at least the catheter will be provided in a sterilized condition. Other kit components, such as a guidewire, may also be included.